A number of physiological parameters are measured to estimate the state of health of a person. In the case of a patient in a hospital and especially in an intensive care unit (ICU) physiological parameters are measured on a continuous basis to monitor variations in the state of health of the patient. This is done to ensure timely medical intervention in case of deterioration in the state of health, especially when the deterioration is likely to endanger life.
One of the important parameters measured is the breathing rate, also called the respiratory rate. The most commonly used method in low acuity settings is to observe the rise and fall of the patient's chest during breathing and counting the number of inhalation and exhalation cycles, timed with a clock. This is problematic when the patient has irregular or shallow breaths due to breathing distress.
Devices and methods to automatically measure the breathing rate are known in the field, using different types of transducers. Some of those methods are impedance plethysmography, capnography (mainly used in ICUs) and inductive thoracic plethysmography (Respiband™) in sleep studies (polysomnography). All these methods require the positioning of the sensor on the patient's body or elsewhere by a trained person.
The published patent application US20100222687, assigned to the same assignee as that of the present application discloses a method of using a plurality of Doppler radars disposed on the seat belt or integrated into the seat belt for monitoring vital body signs of a person seated in a seat of a motor vehicle. The disclosed method unobtrusively monitors vital body signs like heart rate and respiration rate of the person seated in the motor vehicle.